LONDON (Reuters) - The jewellery industry’s standards watchdog, the Responsible Jewellery Council (RJC), is failing to ensure gold and diamonds are responsibly sourced by its members, a campaign group said in a report on Thursday.

U.S.-based Human Rights Watch said the RJC, a standards and certification body founded in 2004 by 14 companies and trade associations, offered only a “weak assurance” that responsible sourcing standards were being met.

“Membership of the RJC ... is no guarantee that a company’s jewellery is responsibly sourced,” it said. “The RJC’s governance, standards, and systems of audit are flawed, allowing companies to be RJC certified even if they fail to meet basic human rights standards.”

The RJC has more than 1,000 members across the jewellery supply chain, from mining companies to retailers. It produces a basic code of practices covering responsible business methods, and a supply chain standard.

“Human Rights Watch (HRW) research has shown that certified RJC members can source gold or diamonds mined under abusive conditions, even as they were deemed compliant with the RJC’s standards,” HRW said.

A spokesman for the RJC said it had reviewed the report, and rejected the allegations that the watchdog had flawed standards, governance and certification systems.

“In their correspondence with the RJC, Human Rights Watch have themselves recognised that the RJC has helped make jewellery companies ‘aware of the importance of responsible sourcing and adopt more responsible practices’,” the spokesman said.

“The standards themselves are internationally recognised as robust and are continually open to comprehensive and transparent review to ensure they continue to advance the cause of responsibility in the industry.”

RJC-accredited suppliers have to pledge they conduct strong human rights due diligence, but do not have to provide evidence, HRW said, while jewellers do not have to demonstrate traceability or chain of custody for their gold or diamonds.

In a recent investigation of the industry’s commitment to ensuring a responsible supply chain, HRW said it found many jewellers relied too heavily on RJC standards.

None of the jewellers, accounting for $30 billion in annual revenue, or 10 percent of global jewellery sales, that the group assessed in its most recent research met the full HRW criteria for responsible sourcing, it said.

“Some of the jewellery companies examined have made important efforts to responsibly source their gold and diamonds, while others have taken much weaker measures, or disclose nothing about their efforts to source gold and diamonds responsibly,” it said in the report.